R&D Report 1954-35 : The subjective grey scale related to television transfer characteristics. M. Gilbert A physiological scale of subjective impressions of brightness is measured in terms of physical scales of luminance. It is found that four criteria of brightness are fairly uniformly spaced along the physical scale when luminance is expressed in logarithmic units. The report confirms that it is preferable to plot the transfer characteristic of a television system in logarithmic units rather than linear units. Quantitative data are presented on the extent of the various regions in the grey-scale for a range of surround adaptations.